Method and apparatus for encoding video with dynamic quality improvement

Patent metadata

Field	Value
Publication number	US-9749638-B1
Application number	US-201113095971-A
Country	US
Kind code	B1
Filing date	Apr 28, 2011
Priority date	Apr 28, 2011
Publication date	Aug 29, 2017
Grant date	Aug 29, 2017

Abstract

A system and method for encoding a video signal having a sequence of frames including a reference frame and a current frame is disclosed. The method includes encoding at a least a portion of the reference frame using a low-quality encoding scheme and encoding the current frame using the reference frame so that the encoded current frame includes at least one pixel encoded using the low-quality encoding scheme. The method also includes identifying a portion of the encoded current frame that includes at least one pixel encoded using the low-quality encoding scheme. The method also includes encoding the identified portion of the current frame using a high-quality encoding scheme.

First claim

What is claimed is:

1. A method for encoding a video signal having a sequence of frames including a reference frame and a current frame, the method comprising:
encoding at a least a portion of the reference frame using a first encoding scheme, wherein the first encoding scheme is a lossy encoding scheme;
encoding the current frame, wherein at least a portion of the current frame is encoded using the portion of the reference frame so that the encoded current frame includes at least one pixel encoded using the first encoding scheme;
determining, subsequent to encoding the current frame, that a current frame bitrate for the encoded current frame is less than a bitrate threshold; and
performing, while the current frame bitrate is less than the bitrate threshold, one or more iterations of a quality improvement operation that includes:
identifying a portion of the encoded current frame that includes at least one pixel encoded using the first encoding scheme based on a comparison of a current frame bitrate and a bitrate threshold,
encoding the identified portion of the current frame using a second encoding scheme, wherein the second encoding scheme is a lossless encoding scheme, and
updating the current frame bitrate for the encoded current frame.

2. The method of claim 1 , wherein the bitrate threshold is based on a bandwidth available for transmitting the encoded current frame.

3. The method of claim 1 , wherein identifying the identified portion of the current frame that includes at least one pixel encoded using the first encoding scheme comprises:
dividing the current frame into a first set of visual quality portions;
identifying a visual quality portion of the first set of visual quality portions as a low-quality or high-quality visual quality portion based on whether there is at least one pixel encoded using the first encoding scheme in the visual quality portion; and
selecting the identified portion of the current frame as one of the low-quality visual quality portions identified in the first set of visual quality portions.

4. The method of claim 3 , wherein identifying the identified portion of the current frame that includes at least one pixel encoded using the first encoding scheme further comprises:
identifying a visual quality portion as low-quality if any pixel in the visual quality portion was encoded by referencing a previously encoded pixel encoded using the first encoding scheme.

5. The method of claim 1 , wherein encoding the current frame comprises:
encoding a reference portion of the current frame by referencing pixels in the reference frame; and
encoding a remainder portion of the current frame using an encoding scheme.

6. The method of claim 1 , further comprising:
identifying an identified portion of the reference frame that includes at least one pixel encoded using the first encoding scheme; and
identifying an identified portion of the current frame that includes at least one pixel encoded using the first encoding scheme using the identified portion of the reference frame.

7. The method of claim 1 , wherein encoding the identified portion of the current frame using a second encoding scheme comprises:
appending the encoded identified portion of the current frame to the encoded current frame.

8. The method of claim 1 , wherein encoding the identified portion of the current frame using a second encoding scheme comprises:
re-encoding the current frame using the second encoding scheme for the identified portion of the current frame; and
replacing the encoded current frame with the re-encoded current frame.

9. The method of claim 1 wherein the first encoding scheme is a low-quality encoding scheme having a greater degree of data loss than a high-quality encoding scheme.

10. The method of claim 1 wherein the second encoding scheme is a high-quality encoding scheme having a lesser degree of data loss than a low-quality encoding scheme.

11. An apparatus for encoding a video signal having a sequence of frames including a reference frame and a current frame, the apparatus comprising:
a memory; and
a processor configured to execute instructions stored in the memory to:
encode at a least a portion of the reference frame using a first encoding scheme, wherein the first encoding scheme is a lossy encoding scheme;
encode the current frame, wherein at least a portion of the current frame is encoded using the portion of the reference frame so that the encoded current frame includes at least one pixel encoded using the first encoding scheme;
determine, subsequent to encoding the current frame, that a current frame bitrate for the current frame is less than a bitrate threshold; and
perform, while the current frame bitrate is less than the bitrate threshold, one or more iterations of a quality improvement operation in which the instruction stored in the memory cause the processor to:
identify a portion of the encoded current frame that includes at least one pixel encoded using the first encoding scheme based on a comparison of a current frame bitrate and a bitrate threshold,
encode the identified portion of the current frame using a second encoding scheme, wherein the second encoding scheme is a lossless encoding scheme, and
update the current frame bitrate for the encoded current frame.

12. The apparatus of claim 11 , wherein the bitrate threshold is based on a bandwidth available for transmitting the encoded current frame.

13. The apparatus of claim 11 , wherein the processor's configuration to identify the identified portion of the current frame that includes at least one pixel encoded using the first encoding scheme comprises instructions to:
divide the current frame into a first set of visual quality portions;
encode a visual quality portion of the first set of visual quality portions as a low-quality or high-quality visual quality portion based on whether there is at least one pixel encoded using the first encoding scheme in the visual quality portion; and
select the identified portion of the current frame as one of the low-quality visual quality portions identified in the first set of visual quality portions.

14. The apparatus of claim 13 , wherein the processor's configuration to identify the identified portion of the current frame that includes at least one pixel encoded using the first encoding scheme further comprises instructions to:
encode a visual quality portion as low-quality if any pixel in the visual quality portion was encoded by referencing a previously encoded pixel encoded using the first encoding scheme.

15. The apparatus of claim 11 , wherein the processor's configuration to encode the current frame comprises instructions to:
encode a reference portion of the current frame by referencing pixels in the reference frame; and
encode a remainder portion of the current frame using an encoding scheme.

16. The apparatus of claim 11 , wherein the processor is further configured to execute instructions stored in the memory to:
identify an identified portion of the reference frame that includes at least one pixel encoded using the first encoding scheme; and
identify an identified portion of the current frame that includes at least one pixel encoded using the first encoding scheme using the identified portion of the reference frame.

17. The apparatus of claim 11 , wherein the processor's configuration to encode the identified portion of the current frame using a second encoding scheme comprises instructions to:
append the encoded identified portion of the current frame to the encoded current frame.

Assignees

• Jia Wei
• Google Inc

Inventors

• Jia Wei

Classifications

• H04N19/147 Primary

  according to rate distortion criteria (rate-distortion as a criterion for motion estimation H04N19/567) · CPC title

• H04N19/154

  Measured or subjectively estimated visual quality after decoding, e.g. measurement of distortion (use of rate-distortion criteria H04N19/147) · CPC title

• H04N19/136

  Incoming video signal characteristics or properties · CPC title

• H04N19/164 Primary

  Feedback from the receiver or from the transmission channel · CPC title

• H04N19/176

  the region being a block, e.g. a macroblock · CPC title